Inserter systems, such as those applicable for use with the present invention, are typically used by organizations such as banks, insurance companies and utility companies for producing a large volume of specific mailings where the contents of each mail item are directed to a particular addressee. Also, other organizations, such as direct mailers, use inserts for producing a large volume of generic mailings where the contents of each mail item are substantially identical for each addressee. Examples of such inserter systems are the 8 series, 9 series, and APS™ inserter systems available from Pitney Bowes Inc. of Stamford, Conn.
In many respects, the typical inserter system resembles a manufacturing assembly line. Sheets and other raw materials (other sheets, enclosures, and envelopes) enter the inserter system as inputs. Then, a plurality of different modules or workstations in the inserter system work cooperatively to process the sheets until a finished mail piece is produced. The exact configuration of each inserter system depends upon the needs of each particular customer or installation.
Typically, inserter systems prepare mail pieces by gathering collations of documents on a conveyor. The collations are then transported on the conveyor to an insertion station where they are automatically stuffed into envelopes. After being stuffed with the collations, the envelopes are removed from the insertion station for further processing. Such further processing may include automated closing and sealing the envelope flap, weighing the envelope, applying postage to the envelope, and finally sorting and stacking the envelopes.
In an insertion system, the detection of the inserts or pack's entry into the envelope is customarily done based on the “time of flight” of a trail edge of the pack to be inserted off of a sensor in the mail path. Because the envelope exists in the same spatial region as the pack to be inserted, a direct detection of the trail edge at the crease line is not performed. As a result, a small amount of extra “overdrive” time must be added to the machine cycle to ensure that the pack is fully inserted. In addition, insertion crashes can occur downstream of the trail edge signal, and improperly inserted collations can be exited from the system.
Thus, a disadvantage of the prior art is that some “open-loop” insertion systems must continue the drive to the pack off of an upstream sensor, and rely on the flight time of the pack, as well as confidence in the insertion system to provide verification that the insertion process has completed successfully. Another disadvantage of the prior art is that additional time must be included in all insertion cycles to allow for the overdrive of the insert.
In an insertion system, the detection of the inserts or pack's entry into the envelope may be done by a thru-beam light emitting diode (LED) sensor. The proper current drive level for a LED component of the sensor system must be set to allow the sensor to see through the flap and detect the insert as the insert enters the envelope. The drive current to the LED component of the sensor system must be set quickly after the envelope is parked at the insertion position and before the insert is inserted into the envelope. When a new current drive level is set the photo transistor component of the sensor system and the LED component of the sensor system must be allowed to stabilize before a measurement of the phototransistor current is made to determine if the LED light source intensity has been increased sufficiently to illuminate through the envelope flap. In this state an insert entering the envelope will decrease the illumination on the phototransistor and cause a measurable decrease in the photo transistor current. Because of the stabilization time, a linear search from low current to high current will take too long to identify the light transmission threshold. It is to be noted that a fixed current value applied to the LED does not create a consistent transmission of light because of variations from one envelope type to another envelope type, i.e., a white envelope to a kraft envelope, etc.
Variations in the light emission and reception properties of the sensor components and supporting circuitry may also prohibit the use of a fixed current value.
Thus, another disadvantage of the prior art is that linear search techniques are too slow and fixed value techniques are unreliable due to the variations described above,